Apparatus for printing positives of a coloured negative



Feb. 19, 1963 T. P. J. BOTDEN ,0

APPARATUS FOR PRINTING POSITIVES OF A COLOURED NEGATIVE Filed Dec. 4. 1957 2 Sheets-Sheet 1 I I Rl02 INVENTOR THEODOOR PETER JCHANNES BOTUEN BY 97 g AGEN Feb. 19, 1963 "r. P. J. BOTDEN 3,077,823

APPARATUS FOR PRINTING POSITIVES OF A COLOURED NEGATIVE Filed Dec. 4, 1957 2 Sheets-Sheet 2 b 25 9 I m I m\ 250 r 24 r 22b, 23b m 21g, 239 I Mr, 22r

B121 B122 y BI23 21 22 23 V II 26 4h 6lr M90 INVENTOR THEODOOR PETER JOHANNES BOIDE BY M E.

AGEN

States 3,077,823 APPARATUS FOR PRINTING PITIVES DE A CQLOURED NEGATIVE Theodoor Peter Johannes Botden, Eindhoven, Netherlands, assignor to North American Philips Company,

Inc New York, N.Y., a corporation of Delaware Filed Dec. 4-, 1957, Ser. No. 7%,669 6 Claims. (Ci. 95-73) The invention relates to a method of printing a positive of a coloured negative by means of at least one the use of the filters, the spectral distribution of this light being varied until the desired colour reproduction of the test positive is obtained. Subsequently, the ultimate positive of the coloured negative is printed with the spectral distribution of the light which has been made to conform with this desired colour reproduction.

Thus, in this'method, a positive of the coloured negative is printed with an approximate spectral distribution of the luminous flux. Subsequently, the colour reproduction of this positive is examined and corrected by changing the spectral composition of the luminous flux.

vIf in accordance with one embodiment of the invention, use is made of socalled absorption filters, that is to say, filters which pass light of a given wave-length range only and absorb the remainder, the absorption filter is adjusted so that the desired colour reproduction of the test print is obtained, after which it must be ascertained, with respect to this new position of the filter, what position of the filter should be used in order to ensure the same colour reproduction of the ultimate positive, for, in this embodiment of the invention, use must be made of complementary colours.

This conversion into complementary colours is eliminated in a further embodimentof the invention. In this further embodiment, the colour filters used in carrying out the method in accordance with the invention are constituted by differently coloured colour-selective interference filters. In this embodiment, the test positive is printed by means of the light passing through the filters, the ultimate spectral composition of the light used to make the ultimate print being determined by correcting the colour reproduction of the test print with the aid of the light reflected by the colour-selective filters. Consequently, this method has the advantage that the test print can be examined concerning the corrections to be made in the spectral composition of the luminous flux to be used in making the ultimate print, by making good any defects in the colour reproduction of the test print by supplying light of the deficient colour, the correction in the complementary colours being simultaneously made in the luminous fluxes passed by the filters. Consequently, this improved method does not require conversion into complementary colours.

As the colour-selective filters, use is preferably made of dichroic mirrors.

According to some embodiments of the invention, the variation in the luminous flux can be obtained by render ing adjustable the effective luminous intensity of one or a number of the light sources used, preferably individually. ,It is also possible to provide means by which, with a fixed adjustment of the luminous intensity of the ice light sources, the amount of light passed by each filter is adjustable.

In general, use will be made of colour-selective filters for the fundamental colours blue, green and red. Use may, for example, be made of three filters, each of which co-operates with a separate light source, the luminous intensity of-which is adjustable. Satisfactory results can also be obtained by the use of a simpler arrangement which comprises only two differently coloured colourselective filters, each of these filters passing one of the fundamental colours blue, green or red, two light sources being arranged symmetrically on both sides of each filter.

In order that the invention may be readily carried out, threeembodiments thereof will now be described more fully, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a longitudinal sectional view of a first embodiment of an arrangement in accordance with the invention.

FIG. 2 is a cross-sectional view of this arrangement taken alongthe plane IlIl of FIG. 1,

FIG. 3 shows, with a view to a better understanding of FIGURES 4 and 5, the manner in which a colourselective interference filter passes or reflects light of certain wave-length ranges,

FIG. 4 shows an embodiment of the arrangement in accordance with the invention in which use is made of three light sources and three colour-selective interference filters, and

FIG. 5 is a structurally simpler embodiment, in which only two colour-selective interference filters are used, which each co-operate with two symmetrically arranged light sources.

In the drawings, it is assumed that the light sources used emit light throughout the entire visible spectrum. It is also assumed that each absorption or interference filter invariably passes one or" the fundamental colours blue, green or red, these fundamental colours being matched as accurately as possible to the fundamental-colour sensi tivity of the photographic material used. In the absorption filters used in the embodiments-shown in FIGURES 1 and 2, the colour passed by each filter is indicated by a capital letter B, G or R, which means thatthis filter passes only the fundamental colour blue, green or red and absorbs the remaining wave-length ranges. In the embodiments shown in FIGURES 3, 4 and 5, the interference filters are also indicated .by one of the capital letters B, G and R. This means, that the filter concerned reflects one of the colours blue, green or red and passes the other wave length ranges.

Furthermore, in FIGURES 3, 4 and 5, the blue, green and red parts of the visible spectrum are designated by a reference numeral followed by one of the small letters b, g or r, which indicate that the spectral part concerned is blue, green or red.

In the embodiment shown in FIG. 1, a housing 1 contains a source of light 2 which co-operates with a reflector 3 and emits light substantially downwards. In order to obtain a diffuse luminous flux, the light source may have a diffuse bulb or (and) use may be made of a separate diffuse filter. The housing 1 has a partition 4 with a central rectangular aperture 5. In the lower part of the housing, provision is made of a support 6 for a coloured negative 7 and a support 8 for a sheet of printing paper 9. .For the sake of clarity, the negative and the printing paper are shown spaced in FIG. 1, and in FIGURES 4 and 5 to be described hereinafter. In actual fact, the negative and the printing paper are in contact with one another. The lower part of the housing 1 also has a door 10.

The partition 4- carries a holder 11 which, within a light-impermeable edge, contains contiguous filters B12, G13 and R14. The transverse dimensions of each of aor'zasas these filters are chosen so that they correspond with the transverse dimensions of the aperture in the partition 4. By means of knobs I5 protruding from the housing 1, the holder Ill can be moved over the partition 4 in the directions indicated by the arrows X-X and YY so that not only each of the absorption filters B12, G13 and R14 can be moved as a whole to register with the aperture 5, but also all intermediate positions, for example the one shown in FIG. 2, are possible. Obviously, precautions are taken to prevent any spurious light from penetrating into the light-tight housing 1 through the apertures formed in its walls for the passages of the rods of the operating knobs 15.

If, now, by means of this arrangement, a positive is to be printed from a coloured negative, a sheet of unexposed printing paper 9 is arranged on the support and the coloured negative is arranged on the support 6. Subsequently, the frame 11 is moved to a position such with respect to the aperture 5 in the partition 4 that, when the lamp is switchesd into circuit, there is at the negative '7 a spectral composition of the light which substantially corresponds with the spectral composition of the light by which the ultimate print is to be viewed. This composition will generally be that of white light, which may correspond to day-light or artificial light. By switching the lamp 2 into circuit, a print is made with the chosen adjustment of the filter. When this print is fixed, it will generally be found that the colour reproduction falls short of expectations. This test print is again arranged on the support 8 and, the negative '7 being removed, viewed by the light of the light source 2 which passes through the filter shown, the colours being corrected by moving the support ll over the partition 4. f, for example, the blue colour is dull in the print a better colour reproduction will be achieved by a blue illumination of higher intensity. In making a subsequent print, with this arrangement a comparatively larger amount of the complementary colours green and red and a smaller amount of blue must be added to the luminous flux by which the ultimate print is exposed, for, due to the negative-positive effect occurring in exposing the printing paper, these complementary colours added to the negative will result in the desired colour in the print. When the test print has been made with the arrangement of the filter as shown in FIG. 2, this colour change in the ultimate print can be achieved by moving the frame 11 to the left over the partition 4 in the same ratio with respect to the relative luminous intensity as has been found in the visual correction of the colour reproduction of the test print. Although satisfactory results can be obtained with this arrangement, its operation requires a certain amount of calculation.

This disadvantage is entirely eliminated if the absorption filter is replaced by a colour-selective interference filter, the operation of which will be briefly explained with reference to FIG. 3.

In FIG. 3, reference numeral 1%; designates the light source which emits light throughout the entire visible spectrum, the fundamental parts of this light being designated 161b, ltillg and 1M1. This light falls on an interference filter R102 which is colour-selective for the colour red. Consequently, the red component 1011- of the light from the light source 101 is reflected; the blue and green components of this light, which are designated will; and 101g respectively, pass through the interference filter R102 and fall on a colour negative 163 as a luminous flux 3101b, and 101g. This negative 103, which shows a certain pattern in colours, in its parts containing green and blue respectively passes the green and blue light respectively. Owing to the absence of the red colour component in the luminous flux Ed th-JAIN), no light passes through the red-coloured parts. The luminous flux 1tl4b1ti4g, which passes through the negative 103 and is modulated according to the pattern thereof, now arrives at the colour-sensitive photographic printing material 165. At the points at which this material is exposed by green and (or) blue light; it is (also) coloured red. The higher the intensity of the illumination by the light source 101, the higher is not only the degree of red coloration of the printing material, but also the intensity of the red component ltllr reflected by the interference filter R102. In the arrangement shown in FIG. 3, the colour component 1911' is available as a reference colour for determining the colour reproduction in red of the print 165 to be made. This fact is used in the embodiment of the method in accordance with the invention shown in FIG. 4. In this embodiment, use is made of three light sources 21, 22 and 23, which as a rule are arranged on a circle but here, for the sake of simplicity are all shown in the plane of the drawing. Each of these light sources co-operatives with a separate colour-selective interference filter B121, G122 and R123.

The arrangement also includes a support 24a for a coloured negative 24, a support 25a for a print to be made and a support 26a for a test print 26 already made.

With the aid of the explanation given with reference to FIG. 3, it will be appreciated that the luminous fiuxes, which are designated I, II and III in FIG. 4, comprise the components indicated in the circumscribed areas. The spectral composition of the luminous flux II, which exposes the print 25 to be made, is the same as that of the luminous flux III which illuminates a finished test print. The luminous intensity of each light source 2]., 22 and 23 can be adjusted individually.

When making a print of a coloured negative 24, a sheet of printing paper 25 which constitutes the light-sensitive support is arranged on the support 25a. The intensity of the light sources 21, 22 and 23 is adjusted so that at the point at which a test print 26a can be arranged, white light is produced of the composition by which the colour reproduction is to be examined. After the print made has been fixed, it is arranged on the support 26a and viewed with the chosen adjustment of the light sources 21, 22 and 23. Usually, the colour reproduction of this print will not be entirely satisfactory. Now the intensity of one or more of the light sources 21, 22 and 23 is adjusted so that the colour reproduction of the test print 26 is correct. Subsequently, the required prints are made with this new adjustment of the light sources 21, 22 and 23; a print made on the support 25 after exposure through the negative 24 will now show exactly the same colour reproduction as the test print arranged on the support 26a, which colour reproduction was corrected by adjustment of the light sources 21, 22 and 23, for, if the colour green was initially too faint in the test print and therefore this colour component has been intensified by increasing the intensity of the light emitted by the light source 22, this results not only in a higher content of green light in the luminous flux III, but also higher contents of blue and red light in the luminous fluxes I and II with a resultant higher amount of green light in the print.

In the embodiment shown in FIG. 5, there are only two colour-selective interference filters R51 and G81, the former co-operating with symmetrically arranged light sources 31 and 41 and the latter co-operating with the similarly arranged light sources 61 and 71. Similarly to what has been described with reference to FIG. 4, a coloured negative 93 is arranged on a support 92, a sheet of printing paper on a support 94 and a test print 1 on a support 90. The luminous fluxes IV, V and VI shown in FIG. 5 have the compositions indicated in the circumscribed areas.

In this arrangement also, the luminous intensities of the light sources 31, 41, 61 and 71 are adjustable individually.

According to a further embodiment of the invention, a measuring device may be arranged at the point of the print of the print 95 in order to determine the luminous intensity at this point.

In the embodiments shown in FIGURES 4 and 5, use may, if required, be made of an additional filter in order to achieve better matching between the composition of the light supplied to the negative and the colour-sensitivity of the photographic material. This additional filter must, in this event, be disposed in the light path between the sources of light and the printing material, not only when making the test print but also when making the ultimate print. It can be removed when the colour reproduction is examined.

What is claimed is:

1. A device for obtaining a color corrected positive color contrast from a negative color contrast comprising at least one light source, a plurality of color selective interference filters of different spectral composition in the path of light rays from said light source, means for adjusting the luminous intensity of the light rays received by said filters from said light source, said latter means including means to divide the light rays into two portions, one of which is transmitted through said filters and the other of which is transmitted in a direction opposite from the filters, means to support a negative color contrast in the path of light rays transmitted through said filters, means to support a photosensitive material for making a positive color contrast in the path of light rays transmitted through the negative color contrast, and means to support a positive color contrast in the path of light rays travelling in the direction opposite from the filters whereby the spectral distribution of the positive contrast can be observed and the luminous intensity of the light rays reaching the filters adjusted to obtain a desired spectral distribution for exposing the light sensitive material.

2. A device as claimed in claim 1 which includes three separate light sources and three color selective interference filters each associated with one of said light sources.

3. A device as claimed in claim 2 in which the filters are dichroic mirrors.

4. A device as claimed in claim 3 in which the filters correspond to the primary colors blue, green, and red.

5. A device as claimed in claim 1 which includes two filters each of which includes two filter elements, each of said filter elements transmitting one of the primary colors blue, green and red, and two light sources symmetrically positioned on both sides of each filter.

6. A device as claimed in claim 1 in which a color correcting filter is interposed between the light-source and the photosensitive material.

References Cited in the file of this patent UNITED STATES PATENTS 2,438,303 Simmon Mar. 23, 1948 2,470,584 Simmon May 17, 1949 2,601,806 Turner July 1, 1952 2,780,155 Debrie Feb. 5, 1957 2,865,245 Kelly Dec. 23, 1958 FOREIGN PATENTS 409,287 Great Britain Apr. 23, 1934 721,547 Great Britain Jan. 5, 1955 

1. A DEVICE FOR OBTAINING A COLOR CORRECTED POSITIVE COLOR CONTRAST FROM A NEGATIVE COLOR CONTRAST COMPRISING AT LEAST ONE LIGHT SOURCE, A PLURALITY OF COLOR SELECTIVE INTERFERENCE FILTERS OF DIFFERENT SPECTRAL COMPOSITION IN THE PATH OF LIGHT RAYS FROM SAID LIGHT SOURCE, MEANS FOR ADJUSTING THE LUMINOUS INTENSITY OF THE LIGHT RAYS RECEIVED BY SAID FILTERS FROM SAID LIGHT SOURCE, SAID LATTER MEANS INCLUDING MEANS TO DIVIDE THE LIGHT RAYS INTO TWO PORTIONS, ONE OF WHICH IS TRANSMITTED THROUGH SAID FILTERS AND THE OTHER OF WHICH IS TRANSMITTED IN A DIRECTION OPPOSITE FROM THE FILTERS, MEANS TO SUPPORT A NEGATIVE COLOR CONTRAST IN THE PATH OF LIGHT RAYS TRANSMITTED THROUGH SAID FILTERS, MEANS TO SUPPORT A PHOTOSENSITIVE MATERIAL FOR MAKING A POSITIVE COLOR CONTRAST IN THE PATH OF LIGHT RAYS TRANSMITTED THROUGH THE NEGATIVE COLOR CONTRAST, AND MEANS TO SUPPORT A POSITIVE COLOR CONTRAST IN THE PATH OF LIGHT RAYS TRAVELLING IN THE DIRECTION OPPOSITE FROM THE FILTERS WHEREBY THE SPECTRAL DISTRIBUTION OF THE POSITIVE CONTRAST CAN BE OBSERVED AND THE LUMINOUS INTENSITY OF THE LIGHT RAYS REACHING THE FILTERS ADJUSTED TO OBTAIN A DESIRED SPECTRAL DISTRIBUTION FOR EXPOSING THE LIGHT SENSITIVE MATERIAL. 